Mars Observer was designed to carry out a high-resolution photography mission of the Red Planet over the course of a Martian year (687 days) from a 378 x 350-km polar orbit. Mars Observer carried a suite of instruments to investigate Martian geology, atmosphere and climate in order to fill in gaps in our knowledge of planetary evolution. A mere 31 minutes after launch, the new Transfer Orbit Stage (TOS) fired to boost the spacecraft on an encounter trajectory with Mars.

After a 725-million-km voyage lasting eleven months, just two days prior to planned entry into Mars orbit, the spacecraft suddenly fell silent at 01:00 UT on 22 August 1993.

Despite vigorous efforts to regain contact, Mars Observer remained quiet. When the spacecraft did not reestablish command as a result of a stored program that was designed to do so in case of five days of silence, mission planners finally gave up hope on salvaging the mission. The results of a five-month investigation proved to be inconclusive, but one likely cause of the catastrophic failure may have been a fuel line rupture that could have damaged the spacecraft's electronics, throwing the vehicle into a spin.

Before contact with the spacecraft was lost, approximately two months of total data from the gamma ray spectrometer was successfully collected, including spectral observations of one burst.

Editor's Note: This mission profile was adapted from an originally published mission profile in Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24.